The present invention relates to a method of and a system for manufacturing organic EL (Electroluminescence) devices.
The present application claims priority from Japanese Application Nos. 2004-114387 and 2004-244848, the disclosures of which are incorporated herein by reference.
An organic EL device has a basic structure formed by laminating on a substrate a lower electrode, an organic layer containing an organic luminescent layer, and an upper electrode. By applying a voltage between the upper electrode and the lower electrode, electrons will be injected into the organic layer from cathode side formed on one of the upper electrode and the lower electrode, while positive holes will be injected into the organic layer from anode side formed on the other of the upper electrode and the lower electrode. In this way, the electrons and positive holes are recombined with each other within the organic luminescent layer of the organic layer, thereby effecting a light emission.
A method of manufacturing a plurality of the above-descried organic EL devices includes a pre-treating step, a film formation step, and a sealing step. Generally, in the pre-treating step, film formation and patterning are performed on a substrate to form thereon lower electrodes and lead electrodes, followed by forming an insulating layer and performing another patterning on the lower electrodes to divide the same to form a plurality of openings in luminescent areas. In the film formation step, film formation is carried out in the openings of the luminescent areas, so that an organic layer containing an organic luminescent layer (for example, a hole transporting layer, a luminescent layer, an electron transporting layer), as well as upper electrodes, are formed successfully on the lower electrodes, thereby forming a plurality of organic EL devices on the substrate. In the sealing step, a sealing cover or a sealing film is used to seal up the formed organic EL devices so as to protect the organic EL devices from outside air.
In the organic EL device manufacturing method described above, an inspection step is performed to find out inferior products in which organic EL devices do not show a good luminescence characteristic due to poor film formation. Usually, such an inspection step is performed only after the sealing step so as to prevent the formed organic EL devices from being exposed to the outside air during the inspection step. For example, Japanese Unexamined Patent Application Publication No. 2001-291585 has suggested providing an inspection room which is maintained at vacuum or kept in a dried atmosphere, performing an inspection step for examining the luminescence characteristic of organic EL devices after forming upper electrodes (after film formation step), without performing a subsequent sealing step for finding out inferior products.
The inspection step applies a voltage between the lower and upper electrodes so as to investigate a luminescence characteristic. However, with regard to organic EL devices required to provide specific luminescent colors in order to perform color display, the inspection step also checks whether there is a color deviation. Such a color deviation is caused due to a reflection interference of lights which are multiply reflected between the upper and lower electrodes together holding an organic layer therebetween and then emitted outwardly, also due to a fact that the peak wavelength of an emitted light is deviated from that of a desired luminescence color. This has proved to be a trouble which happens when the thickness of the organic layer has not reached a predetermined thickness, regardless of whether a display panel containing the organic EL devices is a bottom emission type or a top emission type.
In order to deal with the color deviation mentioned above, Japanese Unexamined Patent Application Publication No. 2000-294372 has disclosed using a film thickness sensor based on a quartz oscillator, or measuring a fluorescence intensity obtained when irradiating evaporated molecules with ultraviolet rays at the time of vapor deposition, thereby effecting a film formation which can ensure a desired film thickness.
According to the conventional method disclosed by Japanese Unexamined Patent Application Publication No. 2001-291585, since an inspection step is performed after the formation of upper electrodes and since organic EL devices having poor luminescence and color deviation are judged to be inferior, such inferior organic EL devices can be removed prior to a sealing step, thus making it possible to dispense with other subsequent steps. In this way, it is possible to reduce a process loss and improve production efficiency. However, since the inspection step is performed after the formation of upper electrodes, it is impossible to correct a color deviation even if the color deviation is caused due to a film thickness which is deviated from a predetermined film thickness. As a result, those judged to be inferior in an inspection step have to be thrown away. Accordingly, a yield of product will be affected by the precision of film formation in a film formation step, and an increased poor film formation can thus bring about a low yield. Besides, there is also a problem that if a high precision of film formation is realized, productivity will decrease.
Moreover, as shown in Japanese Unexamined Patent Application Publication No. 2000-294372, although the film formation step performs the film formation while at the same time measuring film thickness, not any measuring method is capable of directly measuring the thickness of the organic layer laminated on the lower electrodes, but can only indirectly measure such thickness. As a result, an irregularity is likely to occur in the thickness of an actually formed organic layer due to various conditions, proving itself to be a cause which is responsible for color deviations.